【作者】 杨丽；

【导师】 封继康；

【作者基本信息】 吉林大学 ， 物理化学， 2006， 博士

【摘要】 本论文利用密度泛函方法对过渡金属配合物和低聚物及高聚物发光材料进行了一系列的研究。通过理论计算详细的给出了金属有机配合物及聚合物的平衡几何结构、电子结构、能带、最低激发态的几何构型和吸收、发射光谱等信息,这为探索发光材料的结构-性质间关系的建立奠定了基础,并且为实验研究提供了有价值的理论依据,为进一步探索高效率的发光材料做出了重要贡献。研究了不同的给/吸电子基及扩展共轭平面对两个系列铼（I）的金属配合物的电子和光学性质的影响。计算结果表明,扩大共轭体系使得体系的能隙变窄,吸收和发射光谱发生红移。不同的取代基可以调节金属配合物的电子和光学性质。给电子基使得HOMO-LUMO能隙变宽,吸收和发射光谱蓝移;吸电子基使得HOMO-LUMO能隙变窄,吸收和发射光谱红移。研究了新型的多吡啶和邻二氮杂菲（phen）的杂配体铜（I）化合物[Cu（NN）（POP）]⁺。计算结果表明,在phen的2,9位引入取代基能够提高HOMO-LUMO的能带隙,在4,7位引入取代基对能带隙和前线轨道性质的影响较小。并且,由于空间位阻效应,在2,9位取代使得吸收和发射光谱蓝移。研究了不同的取代基对四配位基N₂O₂支撑的磷光Pt化合物的电子和光学性质的影响。结果表明,π-受体比σ-给体对吸收和发射光谱产生更大的影响,并且,前者使吸收和发射光谱发生红移,后者使它们发生蓝移。更重要的是,引入吸电子基使得低能激发与d-d态之间的能量增加,从而有效地阻止了d-d跃迁引起的非能量辐射的可能性。更多还原

【Abstract】 Recently, the scientific researchers endeavor to design and developmentnew type of luminescent devices with high efficient, high stability, highbrightness. The transition metal materials have good performance, such aslong luminescent life and single color. On the other hand, organic electroniclight-emitting film technology also has many distinguished advantages, suchas low power, easily bending, quick response, broad visual angle, large areadisplay, full emitting color and so on, and they are compatible with manykinds of standard technology and can be made of low-cost light-emittingdevices. So the polymers exhibit strong life in the aspect of planar colordisplay. In this paper, calculations on the electronic ground state were carriedout using density functional theory (DFT). The nature and the energy ofsinglet-singlet electronic transitions have been obtained by TD-DFT/B3LYPcalculations performed on the optimized geometries. The excited geometrieswere optimized by ab initio CIS. Based on the excited geometries, theemission spectra are investigated. The theoretical study shows that bymodification of chemical structures could greatly modulate and improve theelectronic and optical properties of light-emitting materials and contribute toorientate the synthesis efforts and help understand the structure-propertiesrelation of these conjugated materials. The following is the main results:1. Two series of rhenium (I) complexes are investigated to explore theeffects of expanding the ligand π system and different electron-donating andelectron-withdrawing substituents on the modulating the orbital and transitioncharacter. The results show that the absorption bands are blue-shifted whensubstituted by electron-releasing group and they are red-shifted whensubstituted by electron-withdrawing group. The enlarged conjugated structuredecreases band gaps and make the absorption and emission red-shifted.2. A series of new copper(I) mixed-ligand complexes [Cu(NN)POP]BF4have been investigated. The calculated results show that introduction of thegroups at 2,9 positions on phen ligand will lift the energy gaps betweenHOMO and LUMO, whereas introduction of the groups at 4,7 positions havelittle effects on both energy gaps and the characters of frontier orbitals, butmake the orbital characters of lower occupied and higher unoccupied orbitalschange. Substitution on 2,9 positions make both the absorption and emissionspectra exhibit blue-shifted due to steric effects.3. We study the effects of different substituents on platinum (II)complexes supported by tetradentate N2O2 chelates on the electronic andoptical properties. Different substituents can modulate both the absorptionsand emissions, but the π-acceptors have more dramatic effects than σ-donorsubstituents, and the former induces the absorption and emission wavelengthsred-shifted and the latter results in blue-shifted. Most importantly, introductionof the electron-withdrawing groups on the bpy ligand will increase the energygap between the lowest excited state and of d-d state, which prohibits thenonradiative deactivation through the pathways of d-d conversion. Thissuggests that such a theoretical approach may provide useful insight in thedesign of new and more efficient phosphorescence materials.4. We study the ground geometries, electronic structure, energy gap,absorption and emission spectra of polymer PPTZ and the copolymer withfluorene (PFPTZ). The calculated results show that relative to the rigid planarstructures in fluorene ring, the phenothiazine ring has highly nonplanarconformations, which impedes π-stacking aggregation and intermolecularexcimer formation, resulting in identical dilute solution and solid-statephotophysics, which hampers the application of polyfluorenes in PLEDs.Importantly, electron-donating groups PTZ not only enhance the opticalstability and thus increase fluorescence quantum yields, but also improve thehole injection and more efficient charge carrier balance. With the fractions ofthe PTZ increasing, the band gaps decrease and the absorption and emissionspectra exhibit red-shifted.5. The geometries, electronic structures, energy gap, absorption andemission spectra of two series of carbazole copolymers. The calculated resultsshow that more twisted structures are obtained compared with pristinepolyfluorene by the incorporation with 3,6-carbazole units. Importantly, thecombination of carbazole with the fluorene moieties resulted in the raisedHOMO energies and consequently the hole injection was greatly improved.With the increasing carbazole content, energy gap becomes broad and bothabsorption and emission peaks exhibit a blue-shifted. The charge carriersthiophene ring and ethynylene significantly lower the LUMO energies andconsequently increase the EAs, which contribute to the highly improvedelectron-accepting and transporting properties.6. Adding of dimethoxy units breaks the conjugation backbone resulted inthe raised HOMO energies and consequently the hole injection was greatlyimproved and the absorption and emission spectra exhibit blue-shifted. Bycooperation with thiophene ring, which results in the better conformations, theabsorption and emission spectra exhibit bathochrome.7. We study the effects of different electron-donating andelectron-withdrawing substituents on the electronic and optical properties offluorene copolymers. All oligomers investigated show less twisted structurescompared with pristine polyfluorene by the incorporation with anelectron-donating or electron-withdrawing units, 3,4-ethylenedioxythiophene(EDOT), pyridine and 1,3,4-oxadiazole moieties. The combination ofelectron-donating unit EDOT with the fluorene moiety resulted in the raisedHOMO energies and consequently the hole injection was greatly improved.However, even though both kinds of charge carriers will improve theelectron-accepting ability, the results show that electron-accepting moietieswill much facilitate the electron-transporting. Similarly, the combination ofBTP with the fluorene moieties resulted in the reduced LUMO energies andconsequently the electron injection was greatly improved.更多还原